Diamond and diamond-like substances have many properties, such as wear resistance, thermal conductivity, electrical resistivity, acoustic transmission, and corrosion inertness, which make them desirable for a variety of industrial applications. To this end, diamond and diamond-like substances have been incorporated into tools for various purposes such as saw blades, drill bits, and electronic components such as surface acoustic wave filters. Methods for incorporating diamond or diamond-like materials into a tool can include known processes such as chemical vapor deposition (CVD) and physical vapor deposition (PVD).
Various CVD techniques have been used in connection with depositing diamond or diamond-like materials onto a substrate. Typical CVD techniques use gas reactants to deposit the diamond or diamond-like material in a layer, or film. These gases generally include a small amount (i.e. less than about 5%) of a carbonaceous material, such as methane, diluted in hydrogen. A variety of specific CVD processes, including equipment and conditions, are well known to those skilled in the art.
In forming a layer of diamond, or diamond-like material on a substrate using CVD techniques, a plurality of diamond grains, or “seeds,” may be first placed upon the substrate surface. The placement of such seeds may be accomplished using CVD itself such as by applying a voltage bias, by polishing with micron-sized diamond, or by other methods known in the art. These seeds act as diamond nuclei and facilitate the growth of a diamond layer outwardly from the substrate as carbon vapor is deposited thereon. As a result, the growing side of the diamond layer becomes increasingly coarse in grain size, and must ultimately be ground and polished to a smooth finish such as by a mechanical means, in order to be suitable for many industrial applications. However, as diamond and diamond-like substances are among the hardest known materials, such mechanical grinding and polishing is difficult and tedious. Moreover, the cost of polishing often exceeds the cost for making the diamond film itself. In addition, mechanical polishing inevitably introduces micro-cracks or variations on the diamond surface. Such cracks and variations are detrimental to certain applications.
The semiconductor industry has recently expanded efforts in producing semiconductor-on-insulator (SOI) devices. These devices allow for electrical insulation between an underlying substrate and any number of useful semiconductor devices. Typically, these SOI devices can include insulating layers with poor thermal conductivity, high degree of thermal expansion mismatch, and/or difficulties in epitaxial growth of silicon or other semiconductor materials. In light of some of these difficulties, various efforts have explored using diamond as the insulating layer with some success. However, such devices continue to benefit from further improvement such as decreasing manufacturing costs, improving performance, and the like.
As such, SOI devices and methods for making diamond containing SOI devices which have improved performance and reduced production costs continues to be sought.